Resolution optical and ultrasound devices for imaging and treatment of body lumens

ABSTRACT

A rotationally vibrating imaging catheter and method of utilization has an array of ultrasound or optical transducers and an actuator along with signal processing, display, and power subsystems. The actuator of the preferred embodiment is a solid-state nitinol actuator. The actuator causes the array to oscillate such that the tip of the catheter is rotated through an angle equal to or less than 360 degrees. The tip is then capable of rotating back the same amount. This action is repeated until the desired imaging information is acquired. The rotationally vibrating catheter produces more imaging points than a non-rotating imaging catheter and eliminates areas of missing information in the reconstructed image. 
     Rotationally vibrating catheters offer higher image resolution than stationary array catheters and greater flexibility and lower costs than mechanically rotating imaging catheters. 
     The rotationally vibrating array carried on a catheter is vibrated or rocked forward and backward to allow for acquisition of three-dimensional information within a region around the transducer array. 
     The addition of adjunctive therapies to the imaging catheter enhances the utility of the instrument. Examples of such therapies include atherectomy, stent placement, thrombectomy, embolic device placement, and irradiation.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.10/440,742, filed May 19, 2003, now U.S. Pat. No. 7,524,289, which is acontinuation-in-part of U.S. patent application Ser. No. 09/690,795,filed on Oct. 17, 2000, now, U.S. Pat. No. 6,592,526, which is acontinuation-in-part of U.S. patent application Ser. No. 09/632,317,filed on Aug. 4, 2000, now abandoned, which is a continuation-in-part ofU.S. patent application Ser. No. 09/236,936, filed on Jan. 25, 1999, nowU.S. Pat. No. 6,110,121 the entirety of which are hereby incorporatedherein by reference.

FIELD OF INVENTION

This invention relates to improvements in devices for intravascularultrasound (IVUS) and optically guided catheter systems.

BACKGROUND OF INVENTION

Intravascular ultrasound is a rapidly evolving imaging technique mostcommonly employed in coronary and iliofemoral arteries. The techniquehas the potential to facilitate the study of aneurysm progression,atherosclerosis or dissection and to outline the effect of endovascularintervention in more detail than angiography.

The presently used intravascular ultrasound systems fall into twocategories: stationary electronic systems and mechanically drivenrotating transducer systems. In both systems, an acoustic element ortransducer is used to transmit a signal, which impinges upon, andreflects from, surfaces of different acoustic densities, which thesignal encounters. An acoustic transducer receives the reflected wave.These data are sent to a processing system via an electrical cable wherethey are manipulated and displayed as an image. The systems are mountedto catheters, or axially elongate structures, which are routed throughbody lumens such as arteries to reach the site of imaging.

The non-rotating or stationary catheter of the stationary electronicsystem houses an array of small acoustic elements, which are positionedcylindrically at the catheter tip. After positioning the catheter in avessel, body lumen or cavity, subgroups of acoustic elements togethergenerate an echo image. The spacing between the acoustic elements in thetransducer array creates areas where the acoustic signal is neithertransmitted nor received. When the data is processed, gaps of missinginformation occur, resulting in a poor quality image. The advantage ofthe stationary electronic system is that the catheter is very flexibleand a central lumen is available for guidewire insertion. No distortionof the image, due to inhomogeneous mechanical rotation, is present. Thestationary catheters are reliable and inexpensive but produce a poorquality image.

The mechanical intravascular ultrasound-imaging catheter comprises amechanically rotating catheter shaft with a single ultrasoundtransducer. Either the acoustic element rotates or the acoustic elementis stationary and a mirror rotates. In this manner, the acoustic signalis transmitted and received in a continuous 360-degree sweep. There areno gaps in the data and a higher quality image results. Realizing adriving mechanism while keeping the catheter fully flexible andsteerable as well as miniature are challenging problems. Distortion ofthe image due to an unequal rotation of the element or mirror at thecatheter tip is a limitation of these systems. Advantages of themechanical probes include high-resolution imaging and absence of nearfield artifact. The mechanically rotating devices produce an acceptableimage but are unreliable and expensive.

Both stationary electronic systems and mechanical systems typicallyoperate with acoustic frequencies from 10 to 30 MHz.

Medical interventions are often performed using endovascular techniques.These interventions include balloon dilatation, atherectomy, stent ordevice placement and removal, drug delivery, thrombolytic therapy,thrombectomy, vessel irradiation, embolic device delivery and thermaltherapy by radio waves or microwaves. Guidance of these endovascularinterventions is preferably accomplished using intravascular ultrasoundimaging.

SUMMARY OF INVENTION

An embodiment of the invention comprises a catheter comprising an arrayof ultrasound transducers and actuators along with signal processing,display, and power subsystems. The actuators on the catheter cause thearray to oscillate. This allows the array to produce more imaging pointsof the object to be viewed than a non-rotating or a stationary array.Additional computer processing of the ultrasound data produces an imagewith a higher resolution than images produced from data from anon-oscillating transducer array.

An embodiment of the invention comprises a catheter, or axially elongatestructure, which has a distal tip and a proximal end. The catheteroptionally comprises a central lumen or a guidewire tip. The centrallumen is often used for guidewire passage. It optionally also comprisesadditional lumens for purposes such as balloon inflation and deflation,stent or embolic device deployment, device retrieval, contrast media ormaterial injection, electromagnetic emissions and drug injection orremoval. The distal tip comprises an array of at least one transducerfor transmitting ultrasound energy radially outward, an array of atleast one transducer for receiving ultrasound signals, and one or moreactuators. The transmitting and receiving transducers is optionally thesame physical entity. The transmitting and receiving transducers areelectrically connected to the proximal end of the catheter by atransmission line, cable or wire bundle, which is electrically connectedto a decoder, a power generator, and a display instrument. The actuatorsare also electrically connected to the proximal end of the catheter witha transmission line, cable or wire bundle, which is electricallyconnected to a power supply. The ultrasound transducer array on thedistal tip of the catheter transmits and receives ultrasound signals,which are processed by a computer to create an image of the objectsubjected to the ultrasound signals.

The transducer array, located near the distal tip of the catheter,rotates clockwise and then counterclockwise either with the rest of thecatheter or, preferably independent of the catheter. The array isrotated through an angle equal to or less than 360 degrees. Mostadvantageously, the array is rotated sufficiently to fill in theinformation gaps but not more than required to minimize the requirementsof the actuator and linkages. The array is then capable of rotatingbackwards the same amount. The net motion is a rotating oscillation or avibration. The oscillating array is optionally covered with anon-oscillating shield. Preferentially, the array will be rotated muchless than 360 degrees so multiple transducers are required in the arrayto maintain a full field of view.

In one embodiment, the distal tip of the catheter comprises an imagingarray that is directed forward as well as the imaging array that isdirected radially outward. The forward directed array allows foracquisition of additional information on the vessel distal to thecatheter. This is especially useful when the radially outwardly directedarray elements are oscillated through too small an angle to gain usefulforward-looking information.

An embodiment of the invention does not continually rotate. It vibratesrotationally in the same manner as an agitator to gather data to fill inthe missing information between array elements. The rotating arrayallows for imaging of a two-dimensional “slice of pie”- or wedge-shapedsegment of the lumen and surrounding tissue. This two-dimensionalimaging region is orthogonal to the axis of the array and generallyorthogonal to the axis of the catheter. By circumferentially vibrating,the array is caused to move to fill in any gaps in information thatexist between adjacent array elements. Lost information between arrayelements is the reason stationary array systems offer less resolutionthan rotating transducer systems.

Since the movement of the array occurs only near the tip of thecatheter, the catheter can be made very flexible up to the point of thearray and, thus, able to negotiate tortuous vasculature. Stiff drivecables used for rotational systems would not pass through tight curvesand could not function distal to serpentine or highly tortuous vascularpathways. The actuators and array of the present invention can be madevery small to accommodate high flexibility requirements of cathetersneeded to navigate tortuous vasculature and still function.

In one embodiment of the present invention, the transducer array isoscillated circumferentially, and in addition, rocked back and forthalong the axis of the catheter to provide imaging information inthree-dimensional space around at least a portion the tip. Actuatorsrotate the array circumferentially as well as axially, with respect tothe axis of the catheter, to create a pyramidal-shaped imaging volumewith a spherical exterior around each transducer of the array. Thethree-dimensional information is also obtainable in a spherical volumearound the transducer array when it is designed with overlapping fieldsof view.

The motion of the imaging transducer array is substantially independentof the motion of the catheter. It is preferable that the catheterremains stationary when the imaging transducer array is in motion sothat a point of reference or baseline is established. The stationarycatheter is generally preferable for therapeutic methodologiesaccomplished under the guidance of the imaging system.

In one embodiment of the invention, the transducer array is oscillatedcircumferentially at a different rate than the rate at which it isrocked back and forth along the plane including the longitudinal axis ofthe catheter. Different oscillation rates ensure that, in the embodimentwhere the two rocking motions are uncoordinated, the transducers imagethe entire potential field rather than just one region. Uncoordinatedmovement is preferable when control and positioning of the transducerarray along one or more axis is difficult or expensive.

In yet another embodiment where the circumferential and axial rockingmotions are coordinated, it is preferable to minimize the total amountof motion of the transducer array to minimize inertial effects andenergy requirements. Thus, it is preferable to rotate in one direction(circumferential for example) fully, increment the position of thesecond direction (axial plane for example) and rotate thecircumferential plane back to its initial position. By repeating thismotion, a zig-zag or serpentine pattern is established throughout thepotential imaging region to provide total or maximal coverage. Once theaxial movement has reached its maximum, the axial actuator moves thetransducer array back to its starting position.

General medical or endovascular use of the vibrating imaging arraypermits three-dimensional imaging to occur without the need to move thecatheter or array as is required for 3-D pullback techniques. The eventsthat are being monitored are, in some cases, generally static, as in aperipheral blood vessel, or the events are more dynamic such as valveand wall motion in the heart, itself. Static imaging, or that used toguide therapy, can use a slower image refresh rate. Thus, for example,an image created by 256 circumferential lines of resolution by 256 axialplanar lines of resolution would want to refresh quickly enough torecord the event being monitored. For the generally static system, thesystem might cycle back and forth circumferentially at 100 Hz, thusmaking a complete axial planar traverse in 1.28 seconds. Refresh ratesas slow as one every five or ten seconds are also useful in certainapplications. Such image refresh rates are appropriate for many medicalapplications. In the heart or during device deployment, however, it isgenerally appropriate to oscillate more quickly so that a full image isobtained in time frames ranging from less than 0.10 second to around 1.0second.

The preferred embodiment for vibrating or agitating the distal tip ofthe catheter is a nitinol actuator or sets of nitinol actuators mountedto cause movement of the transducer array. When the nitinol is exposedto electrical current, it changes dimensions due to resistive heating.When the electric current is removed, the nitinol returns to itsoriginal dimensions. Allowance for hysteresis should be made to accountfor differences in the heating and cooling curves of the nitinol. Bycounter-attaching the actuators, they can be alternately activated anddeactivated causing the transducer array to alternately vibrateclockwise and then counterclockwise or to pivot forward and backwardaxially. This type of actuator is used for back and forth motion of thearray along the axis of the catheter as well as circumferential motion.The actuator set, in one embodiment, is built with separate actuators oras a single system capable of moving the array through two-dimensions tocreate the three-dimensional image. Counter-attached actuators couldalso be replaced with a single actuator using a spring return or othermechanism to ensure correct reverse motion when the power is turned offto the single actuator.

In another embodiment, the invention includes apparatus for cutting orexcising atheroma, thrombus or other tissue from the interior of thebody vessel or lumen. This apparatus comprises an actuator, which may ormay not be the same as that which drives the imaging array, and cuttingelements that act to cut tissue. The cutting elements are disposedwithin a window on the side of the catheter to perform directionalatherectomy or thrombectomy. The cutting elements, in anotherembodiment, are also disposed in the forward direction to allow forchanneling when the catheter is advanced. The invention also comprisescatheter lumen structures and systems to provide suction to assist inthe removal of the excised material.

In yet another embodiment, the invention comprises apparatus forilluminating the body vessel or lumen with electromagnetic radiation atwavelengths from gamma rays to radio waves. Electromagnetic radiationimaging including that using visible light delivery is accomplishedusing fiber-optic channels to transmit light in the visible, infrared orultraviolet range. Ionizing radiation is, in one embodiment, generatedfrom a radioactive source, such as Iridium 192, Iodine 131, Iodine 125,Palladium 109, Strontium 90, Cobalt 57 and Cobalt 60, mounted to the tipof the catheter. Examples of ionizing radiation are electrons,positrons, beta particles, gamma rays and X-rays. A removable shield isoptionally provided to allow irradiation only at the desired site. Amicrowave, X-ray or radio frequency (RF) wave source is also mounted tothe tip of the catheter. Power for the X-ray source, microwave or RFtransducer is carried through the catheter by an electrical cable, wiresor group of wires.

In another embodiment, the invention comprises a catheter capable ofdeploying or retrieving a device such as a stent, balloon dilator orvaso-occlusive material while monitoring the deployment or its resultwith the imaging array. In this embodiment, the array might be internalto the catheter or external to the catheter. The catheter is optionallyplaced through the lumen of one or more guiding catheters to facilitatemaneuvering of the catheter tip through the vasculature or other bodylumen.

The two-dimensional image is processed and displayed, preferentially inreal time, on a two-dimensional monitor or visual output device. Thethree-dimensional image is processed using standard techniques anddisplayed, preferentially in real time, by mapping the image to atwo-dimensional monitor. Three-dimensional systems such as holographicprojectors or a three-dimensional visual output device allow for fullthree-dimensional modeling. The key to processing of the image iscoordination of instant array element position with its one-dimensionalultrasound mapping information. Moving the transducer in one dimensionmakes a two-dimensional image and moving the transducer in twodimensions results in three-dimensional information.

In yet another embodiment, the imaging catheter uses electromagneticscanning radiation, rather than ultrasound. In a preferred embodiment,the imaging array receives information in the near infrared spectrum.Such devices use technology, which is called optical coherencetomography, and are able to provide images inside the vasculature eventhough the vessel or body lumen is filled with visibly opaque blood.Exemplary devices that image using near infrared frequencies includeU.S. Pat. No. 4,242,706 to McCormack et al., U.S. Pat. No. 5,935,075 toCasscells et al., and U.S. Pat. No. 6,415,172 to Painchaud et al, theentire specifications of each, which are included herein by reference.Combinations of optical and ultrasonic systems are also adaptable tothis system.

In yet another embodiment, the imaging catheter uses either ultrasoundor near infrared to map a feature in the vasculature during placement ofan embolic device such as a coil, a stent, a neck bridge, or anamorphous embolic mass. This methodology is particularly suitable forplacement of devices in the cerebrovasculature to embolize aneurysms ofthe cerebrovasculature. Cerebrovascular aneurysms are typicallyberry-type expansions in a vessel wall that could rupture if notprotected against such systemic blood pressure. Rupture of acerebrovascular aneurysm often can lead to severe neurologicaldysfunction, disability, or death. Biplanar fluoroscopy is currentlyused to guide endovascular treatments of these aneurysms but is unableto reveal the nuances of the anatomy. Such nuances, if undetected, canresult in improper packing of the aneurysm and ultimately lead toaneurysm rupture or additional therapy. The real-time three-dimensionalimaging, in conjunction with embolic device deployment can providecomplete information and confirmation of correct placement. A veryflexible catheter is required to reach the cerebrovasculatureendovascularly since the carotid sinus or vertebral arteries aretypically negotiated to reach the circle of Willis where most of thecerebrovascular aneurysms occur. The carotid sinus and vertebralarteries are highly tortuous so only very small and flexible cathetersare capable of being placed across this area. The vibrational imagingarray of the present invention is capable of such flexibility and smallsize since a rotating mechanical element is not required to pass fromthe proximal to the distal end of the catheter in order to move theimaging array.

An embodiment of the invention, using a solid-state actuator, is morereliable and less expensive than the rotating catheters with a singleacoustic transducer. It can also easily have a central lumen forinstrumentation or for a guidewire. In addition, the present inventionproduces a higher resolution image with fewer gaps in the informationthan the stationary imaging catheters. This invention creates ahigh-resolution ultrasound image with higher reliability and lessexpense than is currently available. This invention has the ability togenerate real-time three-dimensional ultrasound images of the regionsurrounding the acoustic transducers.

Another significant advantage of an embodiment of the invention is itsability to navigate tortuous vasculature in order to reach the site ofthe lesion in the body vessel or lumen. It is, because of its greaterflexibility, useful in catheters used to treat lesions of thecerebrovasculature or distal coronary circulation. Interventionaldevices, delivering therapies such as atherectomy, thrombectomy andirradiation, stent placement or removal, thrombogenic therapy andthrombolytic therapy, guided by this high-resolution ultrasound system,offer improved guidance and precision of placement as well asflexibility at potentially reduced cost and higher reliability than thatobtainable from rotating shaft devices. Thus, this invention fills amarket demand for a high resolution, reliable and inexpensive imagingand therapeutic catheter.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention are described herein. It is to beunderstood that not necessarily all such advantages may be achieved inaccordance with any particular embodiment of the invention. Thus, forexample, those skilled in the art will recognize that the invention maybe embodied or carried out in a manner that achieves one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

These and other objects and advantages of the present invention will bemore apparent from the following description taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention. Throughout the drawings, reference numbers are re-used toindicate correspondence between referenced elements.

FIG. 1 shows the imaging area for a stationary imaging catheterpositioned in a body lumen, according to aspects of an embodiment of theinvention;

FIGS. 2A and 2B show the imaging area for a vibrating imaging catheterof the present invention, positioned in a body lumen, according toaspects of an embodiment of the invention;

FIG. 3 is a schematic view of an intravascular ultrasound catheter withoptional therapeutic apparatus mounted thereto, according to aspects ofan embodiment of the invention;

FIG. 4 is an enlarged detail of the distal tip of the imaging catheterof FIG. 3 illustrating the actuator of the preferred embodiment with aradially directed ultrasound array and an optional forwardly directedultrasound array, according to aspects of an embodiment of theinvention;

FIG. 5 is an enlarged sectional view of the distal tip of the catheterof FIG. 3 illustrating the forward directed and radially outwardlydirected ultrasound transducer arrays, electrical connections and theswivel connection, according to aspects of an embodiment of theinvention;

FIG. 6 is an enlarged view of the distal tip of the catheter of FIG. 3illustrating cutting and suction apparatus for an atherectomy orthrombectomy system, according to aspects of an embodiment of theinvention;

FIG. 7 is an enlarged view of the distal tip of the catheter of FIG. 3illustrating a radio frequency, X-ray or microwave wave source,according to aspects of an embodiment of the invention;

FIG. 8 is an enlarged sectional view of the distal tip of the catheterof FIG. 3 illustrating an ionizing radiation source and an optionalshield or shutter, according to aspects of an embodiment of theinvention;

FIG. 9 is an enlarged view of the distal tip of the catheter of FIG. 3illustrating a fiber-optic transmission system, according to aspects ofan embodiment of the invention;

FIG. 10 is a sectional view of the distal tip of a catheter with animaging array comprising an ultrasound transducer, which is oscillatingcircumferentially as well as axially, according to aspects of anembodiment of the invention;

FIG. 11 illustrates the imaging area of a transducer oscillatingcircumferentially according to aspects of an embodiment of theinvention.

FIG. 12 illustrates the imaging area of a transducer oscillatinglongitudinally along the axis of the catheter, according to aspects ofan embodiment of the invention;

FIG. 13 illustrates the imaging volume of a single transducer arrayoscillating circumferentially approximately 90 degrees and axiallyapproximately 60 degrees, according to aspects of an embodiment of theinvention;

FIG. 14 illustrates the three-dimensional imaging volume of a transducerarray of four transducers oscillating circumferentially 90 degrees andaxially 60 degrees relative to the axis of the catheter, according toaspects of an embodiment of the invention;

FIG. 15 is a sectional view of a catheter tip illustrating an inflationlumen, a collapsed dilatation balloon and a collapsed stent, accordingto aspects of an embodiment of the invention. The catheter also includesthe transducer array and actuators for three-dimensional imaging of thebody lumen or cavity;

FIG. 16 is a view of the catheter tip of FIG. 15 with the dilatationballoon and stent expanded, according to aspects of an embodiment of theinvention; and

FIG. 17 illustrates a sectional view of the catheter tip illustratingdeployment of an embolic coil into an aneurysm, according to aspects ofan embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention herein described is an ultrasound imaging and treatmentcatheter comprising a rotationally vibrating array of ultrasoundtransducers. An embodiment of the catheter allows the flexibility andcost effectiveness of a conventional stationary ultrasound-imagingcatheter but has superior image data gathering capabilities as isillustrated in FIGS. 1, 2A, and 2B.

FIG. 1 illustrates, in cross section, a distal tip of a stationaryimaging catheter 102 imaging a body lumen 100. The body lumen 100 has aninside surface irregularity 110 on a body lumen wall 101. The imagingcatheter 102 comprises a plurality or array of ultrasound transducers104, a plurality of fields of view or imaging areas 106 and a pluralityof blind spots or blind areas 108. Examples of body lumens includearteries, veins, ureters, the bladder, the urethra and biliary ducts.The transducers 104 are placed circumferentially around the tip 102.Each transducer 104 transmits ultrasound energy and receives reflectedultrasound energy within its field of view 106. The blind spots 108 areareas where no ultrasound energy is transmitted nor is any reflectedultrasound energy received. Most of the illustrated lumen irregularity110 is in one of the blind spots 108. After data from the transducers104 is processed to create a visual image, the blind spots 108correspond to areas of no or missing information, resulting in a poorimage.

Referring to FIG. 2A, a circumferentially vibrating portion of a distaltip or end 2 of an imaging catheter images a portion of the body lumen100. The vibrating part of the imaging catheter comprises a plurality orarray of ultrasound transducers 4, and a plurality of fields of view orimaging areas 6. The transducers 4 are placed circumferentially aroundthe tip 2. Each transducer 4 transmits output ultrasound acoustic wavesor energy in response to output or transmission electrical signals andreceives reflected ultrasound energy within its imaging area 6. Thesurface irregularity 110 of the body lumen 100 is not yet in the imagingarea 6 of the transducers 4.

As the array of transducers 4, located within or on the catheter tip 2is circumferentially vibrated, as illustrated in FIG. 2B, thetransducers 4 continue to transmit output ultrasound acoustic waves toand receive reflected ultrasound energy from the body lumen 100.However, each transducer 4 is circumferentially vibrating and shiftedfrom its previous position. The imaging areas 6 overlap, as shown bycomparing FIGS. 2A and 2B. The surface irregularity 110 of the bodylumen 100 is in the field of view or imaging area 6 of the transducers 4after the transducers 4 are circumferentially, or rotationally,vibrated. When the reflection data from the transducers 4 is processed,the resulting visual image has no areas of missing information; thusresulting in a complete image, which is superior to the image producedby a stationary ultrasound catheter.

An embodiment of the device, as shown in FIG. 3, is a catheter 12comprising a catheter shaft 14, a proximal end 16, the distal end or tip2, a central lumen 18 and a wire bundle or transmission line 20.Additional lumens are optionally added for functions such as dye orfluid injection, fluid removal, electrical or electromagnetic energydelivery, atherectomy control, stent or material deployment orretrieval, balloon inflation and/or deflation. The proximal end 16comprises a power/data port 24, a decoder/processor system 26, anultrasound-input signal and power supply/controller 28, an actuatorpower supply/controller 30, and a display device or display monitor 32.The proximal end 16 optionally comprises an inflation port 36, aninflation lumen 350, an inflation system 38 and a guidewire 40. Theinflation system 38 may, for example, be a syringe with or withoutmechanical advantage such as levers or jackscrews. The proximal end 16further optionally comprises an illumination source 218, a power source220 for X-ray, radio frequency or microwave energy and/or a shuttercontroller 222 for an ionizing radiation source. A connector 226 isoptionally provided at the proximal end of the catheter 12 to seal theguidewire 40 entrance against fluid leakage, using a proximalfluid-tight seal 242, and to allow for attachment of a suction device orvacuum source 224 to remove fluid and excised debris from the bodyvessel or lumen. Fluid injection to the body lumen is, for example, forpurposes such as occlusion, chelation, drug delivery or lysis.

Additionally, the distal tip 2 comprises the plurality or array ofradially, outwardly directed ultrasound transducers 4, a circumferentialactuator 42 or, in the preferred embodiment, a nitinol circumferentialactuator 42, and a swivel joint or circumferential rotational bearing44. The distal tip further optionally comprises the other end of thecentral lumen 18, the other end of the guidewire 40, or a balloon 22.The balloon 22 is preferably an angioplasty-type balloon suitable forvessel dilation or stent expansion. Such balloons are made frommaterials such as polyethylene terephthalate (PET), polyimide or otherhigh-strength polymers. The balloon 22 could also be made fromelastomeric materials like polyurethane or latex. Such materials aresuited for centering the catheter tip in the body lumen or vessel.

The distal tip 2 of catheter 12 optionally comprises an array offorwardly directed ultrasound transducers 202. It also optionallycomprises a distal fluid-tight seal 204, which prevents fluid frompassing into the central lumen 18 from the guidewire 40 exit. A cuttingapparatus 208 and a fluid suction or vacuum port 206 are also includedon the oscillating distal tip 2 of the catheter. The distal tip 2 ofcatheter 12 further optionally comprises a wave source 228. Possiblewave sources are X-ray emitters, microwave and radio frequency antennasand ionizing radiation sources.

As shown in FIG. 5, each transducer in the transducer arrays 4 and 202comprises a plurality of transducer leads 48. As shown in FIG. 4, thecircumferential actuator 42 comprises a positive signal/power lead 60and a negative signal/power lead 62. The leads 48, 60, 62 are bundledtogether in the wire bundle or transmission line 20 which travels thelength of the catheter shaft 14 and carries power to the actuator 42 aswell as output and reflection electrical signals to and from,respectively, the acoustic arrays 4 and 202. The central lumen 18 isalso shown.

Referring to FIG. 3, the catheter 12 is positioned in a body lumen orcavity to collect data for an ultrasound image. The lumen wall ideallyfits against the outside of the catheter or is liquid-filled in order toefficiently transmit the acoustic waves. In lumens that are not liquidfilled, the balloon 22 is optionally disposed to surround transducers 4and inflated with liquid to fill the space between the catheter tip 2and wall of the body lumen. The ultrasound array signal and powersupply/controller 28 sends output signals to and receives reflectionsignals from the transducer arrays 4 and 202 over the cable or wirebundle 20. The information from the ultrasound arrays 4 and 202, in theform of reflection electrical signals, is sent to the decoder/processorsystem 26 where the electronic data is processed to compensate forjitter, hysteresis, and uneven rotation. The processed data is sent tothe display monitor 32 where the ultrasound image of the body lumen orcavity is displayed.

While the ultrasound arrays 4 and 202 are receiving and transmittinginformation, the circumferential actuator 42 is receiving controlsignals from the actuator power supply 30. The actuator control signalsare such so as to cause the circumferential actuator 42 to rotate thedistal tip 2 of the catheter 12 through an angle of 360 degrees or lessand then reverse the rotation through an angle of 360 degrees or less.Once the clockwise and counterclockwise rotation cycle is complete, thecycle repeats until the desired data is collected.

In a preferred embodiment, the circumferential actuator 42 utilized torotationally vibrate the distal tip 2 of the ultrasound-imaging catheter12 comprises a nitinol actuator. Nitinol is a nickel-titanium alloy,which, in certain embodiments, exhibits a shape memory effect. Shapememory alloys (SMA) are easily deformed and, when heated, they return totheir original shape. Shape memory actuators fabricated from thin filmor wire can be heated resistively. The small thermal mass and largesurface to volume ratios associated with thin films allow for rapid heattransfer. Switching rates can be in the range of up to about 100 Hz orfaster. Motion rates for transducers 4 ideally will be between 1 Hz and300 Hz and more preferentially between 30 Hz and 200 Hz in order toprovide an image with a minimum of flicker.

FIG. 4 shows the distal tip 2 of the catheter 12 of FIG. 3 with thecircumferential actuator 42 of the preferred embodiment. The distal tip2 of the catheter comprises the central lumen 18 with the guidewire 40,the ultrasound transducer array 4, the swivel joint 44, the wire bundle20 and the nitinol actuator 42. Optionally, the distal tip 2 alsocontains the forwardly directed ultrasound transducer array 202. Thenitinol actuator 42 comprises a mount top 52 and a mount bottom 54, anitinol ligament/element 56, a connection or attachment 58, the positivesignal/power lead 60 and the negative signal/power lead 62. The mountbottom 54 is attached to the catheter shaft 14 while the mount top 52 isattached to the catheter tip 2. The positive lead 60 and the negativelead 62 are attached to opposite edges of the nitinol ligament/element56, respectively.

Referring to FIG. 3 and FIG. 4, the positive lead 60 and the negativelead 62 are routed into the wire bundle or transmission line 20. Thepositive 60 and negative leads 62 exit the wire bundle 20 at thepower/data port 24 where they are connected to the actuator powersupply/controller 30. The actuator power supply/controller 30 transmitsover the transmission line 20 an electrical signal through the leads 60,62 to the nitinol ligament/element 56. This creates either resistiveheating when powered or cooling when power is removed through thenitinol ligament/element 56 which causes the nitinol ligament/element 56to expand or contract its length along the circumference of the distaltip 2.

The nitinol ligament 56 comprises a nitinol film attached to a flexiblesubstrate as described by R. S. Maynard in U.S. Pat. No. 5,405,337. Thenitinol film is deposited onto a corrugated silicon surface coated witha thin layer of silicon nitride giving the nitinol ligaments 56 asinusoidal shape. Polyimide is then spun on and windows are opened toexpose the nitinol element. After dissolving the silicon wafer, theflexible polyimide acts as a support structure for the nitinol ligaments56. While a shape memory alloy actuator is the preferred embodiment,other actuators 42, such as those manufactured with electromagnetic ormechanically driven systems, could also be used. The publishedliterature includes other SMA actuators that are also useable with thisinvention.

Referring to FIG. 3 and FIG. 4, the actuator power controller 30 sends asignal through the positive 60 and negative leads 62 to the SMAligament/element 56 such that the ligament/element 56 becomes heated andcontracts which pulls or rotates the distal tip 2 through an angle of360 degrees or less at the swivel joint 44. Next, the powersupply/controller 30 sends a signal causing the SMA ligament/element 56to cool and stretch, which pulls back or reverses the rotation of thedistal tip 2 through the swivel joint 44. Typically heating is caused byapplying power to the resistive load of the SMA element/ligament andcooling is caused by removing said power. The duty cycle of the signalis set to cause the SMA ligament/element 56 to continuously pull andpush the distal tip 2. The resulting motion is a rotational vibration ofthe catheter tip 2.

In a more preferred embodiment, a plurality of nitinol actuators 42 aredisposed circumferentially around the catheter tip 2. The phases of thecontrolling signals are adjusted such that when one nitinol actuator 42is pulling, the opposing SMA actuator 42 is pushing. That is, when poweris applied across the leads 60 and 62 of the first actuator 42, theelectrical power across the electrical leads 60 and 62 of the second SMAactuator 42 is turned off. In this manner, the rotational vibration ofthe catheter tip 2 can be made steadier and more reliable.

In another embodiment, the actuator 42 is electromagnetic, usingpermanent magnets and electromagnets to oscillate the catheter tip 2.This system is similar to an electric motor in that the polarities areswitched on the electromagnet but continuous rotation is prevented. Theelectromagnetic system can be installed in the catheter tip 2 or it cantransmit the energy through a torque shaft and thus be outside the body.

In yet another embodiment, a mechanical rocker linkage can be used tocause the rotational oscillations.

In another preferred embodiment the tip 2 rotates independently of thecatheter shaft 14. A longitudinal section of the distal tip 2 is shownin FIG. 5. The distal tip 2 comprises the plurality or array of radiallydirected ultrasound transducers 4 and, optionally forwardly directedultrasound transducers 202, the wire bundle 20, the guidewire 40, andthe swivel connection 44. Each transducer 4 and 202 comprises leads 48which are constrained together in the wire bundle 20. The swivelconnection 44 of this embodiment comprises a shaft lip 68, a tip lip 72,and a corresponding void 74. The shaft lip 68, the tip lip 72, and thevoid 74 are annular in configuration. The shaft lip 68 and tip lip 72mate in a non-binding manner with the void 74 between the shaft lip 68and tip lip 72. The shaft lip 68 and tip lip 72 are constructed toretain the distal tip 2 onto the catheter shaft 14. This results in thecatheter shaft 14 retaining the catheter tip 2 but allowing the tip 2 torotate freely on the shaft 14. The wire bundle 20 comprising the leads48, 60, 62 passes through the above described annular swivel joint 44.

In another embodiment, the leads are connected to a swivel jointelectrical rotational connector 44 to allow for the passage ofelectrical signals and power through the swivel joint.

Yet another embodiment of the swivel joint 44 is an elastic segmentjoining the catheter shaft 14 and the catheter tip 2. This segmentabsorbs torque of the oscillating tip 2 and does not transmit therotational vibration through the catheter shaft 14. The catheter shaftcould optionally also include a high inertia region disposed proximal ofthe distal tip to stabilize the proximal portion of the catheter.

A further embodiment of the swivel joint 44 is a rotational bearingsystem. Additionally, the catheter 12 could be so flexible as to notrequire any special swivel connection. Any rotational oscillation wouldbe damped along the length of the catheter shaft 14.

In addition to the guidewire 40 and the balloon 22, other embodiments ofthe catheter 12 include a linear reference transducer, and a rotationalreference transducer. The balloon 22 is used with the ballooninflation/deflation system 38 to center the catheter 12 in a vessellumen. The guidewire 40 is used to guide the catheter to the region tobe imaged. The linear reference transducer is used when performing athree-dimensional pullback image of the vessel lumen. It allows foraccurate determination of location axially along the lumen.

Further, the rotational reference transducer is optionally used tomeasure the rotational displacement between the catheter shaft 14 andthe catheter tip 2. One embodiment comprises a Hall effect switch orother magnetic device where part of the device is attached to thecatheter tip 2 and the remaining part of the device is attached to thecatheter shaft 14. Signals are sent, via the wire bundle 20, containingtip 2 to shaft 14 displacement information. The information is processedand correlated with the ultrasound image. The reference transducers, inanother embodiment, are made from strain-gauge type devices that changeresistance with strain. Such strain gauge or reference transducers couldbe mounted across any part of the catheter that moves, including beingmounted across the actuators to measure contraction and expansion.

Different therapeutic apparatus are optionally incorporated into acatheter that comprises imaging capability. Endovascular treatment ofpatients is becoming more widely practiced and improved guidance ofendovascular therapies would be beneficial to the patient. FIGS. 3, 6,7, 8, 9, 15 and 16 illustrate some of the therapeutic apparatusapplicable to this system.

FIG. 6 shows an enlarged view of the distal tip 2 of catheter 12 withoptional atherectomy or thrombectomy apparatus. Atherectomy and/orthrombectomy may be accomplished using a rotational or vibrating cutterdisposed on the catheter to excise plaque or thrombus. The distal tip 2additionally comprises the distal fluid-tight seal 204, the fluidsuction ports 206 and the plurality of cutting apparatus 208. Thecutting apparatus 208, such as cutting blades or atherectomy cutters,vibrate rotationally under the motion generated by actuator 42.Optionally, the cutting apparatus 208 may be driven by a differentactuator than that used to drive the motion of the ultrasound arrays 4and 202. The distal fluid-tight seal 204 prevents flow around theguidewire 40 exit when vacuum is generated in the central lumen 18. Itallows the vacuum to be directed through vacuum ports 206 to removetissue that has been excised by the cutting blades 208. Referring toFIG. 3, connector 226 seals the central lumen 18 around the guidewire 40entrance using the proximal fluid-tight seal 242, and allows forconnection of the vacuum source or suction device 224.

FIG. 7 shows an enlarged view of distal tip 2 incorporating an optionalwave source 228. These wave sources emit potentially therapeutic energyto the body lumen or cavity. The wave source 228 comprises a wavegenerator 214 and a plurality of electrical leads 216. Possible wavegenerators are an X-ray source such as an X-ray tube, a radio frequencyantenna or a microwave antenna. Referring to FIG. 3 and FIG. 7, theelectrical leads 216 are connected to the wave generator 214 at thedistal tip 2, traverse the catheter 12 through the wire bundle 20 andare connected to the power source 220 at the proximal end 16 of catheter12.

FIG. 8 shows an enlarged sectional view of the distal tip 2 showinganother embodiment of the optional wave source 228. In this embodiment,the optional wave source 228 comprises a radioactive source 234, ashutter 240, a cavity 232, a linkage 236, a flexible connector 230 and alumen 238. The radioactive source 234 provides therapeutic energy, inthe form of ionizing radiation, to the body vessel or lumen. The shutter240 is opened and closed by linkage 236. When the shutter 240 is opened,the radioactive source 234 radiates outward into the body vessel orlumen. When the shutter 240 is closed, the radiation is prevented fromescaping. The cavity 232 provides space for the shutter 240 to open. Thelinkage 236 rides within lumen 238 and is connected across the swiveljoint 44 by the flexible connector 230. Referring to FIG. 3 and FIG. 8,the linkage 236 is connected at the proximal end 16 of catheter 12 tothe shutter controller 222. The radioactive source 234 could bepositioned proximal to the swivel joint 44 to eliminate the need for theflexible connector 230.

FIG. 9 shows an enlarged view of the distal tip 2 of catheter 12comprising yet another embodiment of optional wave source 228. Wavesource 228 comprises, in this embodiment, an optional fiber optic bundle210 and a lens 212. The fiber optic bundle 210 is used to provideillumination of the body lumen or cavity with visible or near visiblelight such as infrared or ultraviolet light. The fiber optic bundle 210is connected to the optional lens 212 to allow for focusing ordispersion of the light as desired. Referring to FIG. 3 and FIG. 9, thefiber optic bundle 210 is disposed along the central lumen 18 of thecatheter 12, so that it is not stressed or flexed by the vibrationalrotation of the catheter distal tip 2. The fiber optic bundle 210 isconnected at the proximal end 16 of catheter 12 to the illuminationsource 218.

FIG. 10 shows an enlarged view of the distal tip 2 of catheter 12comprising elements that allow for three-dimensional imaging of the bodylumen or cavity. The distal tip 2 comprises the catheter shaft 14, anaxial carrier element 302, the array of radially outwardly directedultrasound transducers 4, a circumferential carrier 318, an acoustictransmission fluid 316, an axial bearing 300, the circumferentialrotational bearings or swivel joints 44, a set of at least one axialactuator 304, a corresponding set of axial connector arms 306, thecircumferential actuators 42, a corresponding set of circumferentialconnector arms 312, a set of strain gauges 308 and the wire bundle 20.

As discussed previously, each array of ultrasound transducers 4 comprisethe plurality of transducer leads 48. The circumferential actuators 42and the axial actuators 304 comprise the positive signal/power leads 60and the negative signal/power leads 62. The strain gauges 308 comprise aplurality of strain gauge electrical leads 310. The leads 48, 60, 62 and310 are bundled together in the wire bundle 20 which travels the lengthof the catheter shaft 14 and carries power to the circumferentialactuators 42 and the axial actuators 304 and power/deflectioninformation to and from the strain-gauges 308 as well as output andreflection electrical signals to and from the ultrasound acoustictransducer array 4.

Referring to FIG. 10, the axial carrier element 302 holds the transducerarray 4 within the circumferential carrier 318. The acoustictransmission fluid 316, such as water, fills the space between axialcarrier 302 and circumferential carrier 318 as well as the space betweencircumferential carrier 318 and catheter shaft 14. The bearing 300couples the axial carrier element 302 to the circumferential carrier318. Circumferential rotational bearings 44 couple the circumferentialcarrier 318 to the catheter shaft 14. Axial actuators 304 connect thecircumferential carrier 318 to the rotational carrier 302 through theaxial connector arms 306. Circumferential actuators 42 connect thecatheter shaft 14 to the circumferential carrier 318 throughcircumferential connector arms 312. Strain gauges 308 are connectedacross actuators 42 and 304.

Electrical signal leads 48 connect the ultrasound transducers 4 to wirebundle 20 through swivel joint 44. Positive signal/power leads 60 andnegative signal/power leads 62 connect the axial actuators 304 andcircumferential actuators 42 to the wire bundle 20 through swivel joint44. Strain gauge electrical leads 310 connect the strain gauges 308 tothe wire bundle 20 through swivel joint 44.

Referring to FIG. 3 and FIG. 10, axial carrier 302 holds the transducers4 and is able to move in a rocking fashion around the axis constrainedby bearing 300 to motion in the plane parallel to the axis of thecatheter shaft 14. Bearing 300 is also an optional electrical swiveljoint. Axial actuators 304 move the axial carrier 302 about bearing 300to image in the forward (toward the distal tip) and backward (toward theproximal end of the catheter) direction. Sufficient space should beprovided inside circumferential carrier 318 to allow for the desiredmotion of axial carrier 302. Acoustic transmission fluid 316 is requiredto fill any air gaps that might exist in the catheter tip so that theacoustic signals are not attenuated after leaving transducers 4 orbefore being received by transducers 4. The shapes of thecircumferential carrier 318 and axial carrier 302 are designed tominimize drag and cavitation when operating in the liquid 316. Preferredshapes for the carriers 302 and 318 are cylinders with axes parallel totheir respective bearings 300 and 44 or a single sphere. The spherecould be magnetically levitated within a cavity so no bearing would beneeded. Optional connector arms 306 increase the freedom of motion forthe axial carrier 302. Sufficiently flexible actuators 304 and 42 wouldnot require connector arms 306 or 312, respectively. Strain gauges 308provide positioning information for each of the actuators 304 and 42.The strain gauge 308 information is fed through the electrical lead 310,the swivel joint 44 and the wire bundle 20 to the decoder/processor 26for image analysis. Positioning information is required in order to mapthe transducer output into a two or three-dimensional coordinate system.Actuators 42 move the circumferential array carrier 318 in thecircumferential direction with one rotational bearing 44 shown near thetip of the catheter and another rotational bearing 44 located at thebottom of the circumferential carrier 318. Positive signal/power leads60 and negative signal/power leads 62 provide controlled power to eachof the actuators 304 and 42 through wire bundle 20 from actuator powersupply/controller 30. Transducer leads 48, bearing 300 and electricalswivel joint 44 connect the decoder/processor 26 and ultrasound-inputsignal and power supply/controller 28 through the wire bundle 20 to thetransducers 4.

Actuators 42 and 304 are shown for ease of viewing in the plane parallelto the axis of the catheter shaft 14. One or more actuators 42 and 304could also be mounted in the plane perpendicular to the axis of thecatheter shaft 14. One or both sets of actuators 304 and 42 could bedisposed on a single integrated device to provide motion in both thecircumferential and the forward and backward axial rocking directions.Such orthogonal disposition of some or all the actuators could minimizelongitudinal stiffness in the catheter and maximize flexibility. Inaddition, swivel bearings 300 and 44 could be replaced with a singlebearing operational in two dimensions, rotation and axial. Such abearing would be, for example, a ball in a socket or an elasticcoupling. The axial transducer carrier 302 and the circumferentialtransducer carrier 318 would be integrated into a single unit for thesingle bearing system. In a further evolved embodiment, the transducers4 could be mounted to actuators 304 and 42 such that no pivot bearing isrequired, rather, the transducers 4 would be pivoted directly by theactuators. The transducers 4 could also be moved linearly by theactuators but motion is limited by the travel of the actuators sopivoting allows for increasing the three-dimensional imaging volumewithout a very large amount of actuator travel. The apparatus allows fortwo-dimensional and three-dimensional imaging of a body lumen or cavitywithout the need to move the catheter shaft 14 to obtain some of theimaging information.

In a preferred embodiment, actuators 304 and 42 comprise nitinolactuators. These actuators 304 and 42 operate independently to movetheir respective carriers 302 and 318 about their respective pivotpoints. Each actuator is separately operated or fired. Counter-attachedactuators 304 are energized sequentially to create a rocking motion ofthe axial carrier 318, around axial bearing 300, through axial connectorarms 306. This axial rocking motion is independent of thecircumferential rocking motion generated by actuators 42.Counter-attached actuators 42 would be energized sequentially to createa rocking motion of circumferential carrier 318, around circumferentialbearing 44, through circumferential connector arms 312, Sequentialenergizing of counter-attached actuators involves energizing oneactuator while power to the other actuator is turned off. Various typesof motion could be obtained with this system ranging from random motionto a coordinated scan similar to that used on cathode ray tube screens.Circumferential and axial scan rates of 1 to 400 Hz are appropriate withpreferred ranges of 30 to 200 Hz.

FIG. 11 illustrates, in cross-section orthogonal to the axis of thecatheter, the two-dimensional imaging area of a two-ultrasoundtransducer array 4, rotating or oscillating circumferentially through a90-degree arc. Catheter 12 is inserted into body lumen 100. The tip 2 ofcatheter 12 comprises the array 4 of two ultrasound transducers. Theimage generated by the ultrasound transducer array 4 has a rangeillustrated by a boundary 332. Body lumen 100 comprises the body lumenwall 101, the surface irregularity or atherosclerosis 110, a surroundingtissue 328 and a volume of blood or fluid 330.

The lumen wall 101 is disposed circumferentially around catheter 12,which is centered in body lumen 100. In this embodiment, the array oftransducers 4 is rotated or oscillated only in the circumferentialdirection through a 90-degree angle. A two-dimensional wedge shapedimage of the body lumen 100 is obtained. The wedge is bounded by therange of the transducers 4 and the angle through which the transducers 4are rotated. In this embodiment, the image area comprises two 90-degreewedges. Additionally, there is an area where no information is acquiredcomprising a blind area 320 of two 90-degree wedges. The body lumen wall101, surface irregularity 110, surrounding tissue 328 and fluid 330 arenot visible in the blind areas 320.

The maximum range of the transducers is described by the boundary 332.The distance from the transducer 4 to the boundary 332 and theresolution of the image are affected by the modulation frequency of thetransducer array 4. In general, when the modulation frequency isincreased, the range is decreased and the resolution of the image isincreased. The modulation frequency of the ultrasound system is from 1to 100 MHz, with a preferred range from 5 to 50 MHz and a more preferredrange of 10 to 30 MHz. The practical circumferential angular limit isdetermined by the mechanics and dynamics of the actuators 42 andcircumferential connector arms 312, number of transducers 4, mechanicsof bearings 44 and 300 and the space available within the catheter 12.

FIG. 12 illustrates, in cross-section parallel to the axis of thecatheter, the two-dimensional imaging area of a two-ultrasoundtransducer array 4 rocking or pivoting longitudinally parallel to theaxis of the catheter through a 60-degree arc. Catheter 12 is insertedinto body lumen 100. The tip 2 of catheter 12 comprises the array 4 oftwo ultrasound transducers in axial carrier 302 being rocked aroundaxial bearing 300. Body lumen 100 comprises the surface irregularity oratherosclerosis 110, the surrounding tissue 328 and blood or fluid 330.Fluid 330 fills the image between the body lumen wall 101 and thecatheter 12. The body lumen wall 101 is disposed around catheter 12,which is centered in the body lumen 100. In this embodiment, the arrayof transducers 4 is rocked 30 degrees forward and 30 degrees backward(60 degrees total) in the plane parallel to the axis of the catheter 12.A two-dimensional wedge-shaped image of the body lumen wall 101 isobtained. The wedge is bounded by the range 332 of the transducers 4 andthe angle through which the transducers 4 are rocked. In thisembodiment, the field of view or imaging area comprises two 60-degreewedges. Additionally there is an area where no information is acquiredcomprising the dead or blind area 320 of two 120-degree wedges. The bodylumen wall 101, blood 330 and atherosclerosis 110 are not visible in theblind areas 320.

Referring to FIG. 3 and FIG. 10, the practical limit of the angular tiltof the array of transducers 4 is governed by the mechanics and dynamicsof the bearing 300, the axial carrier 302, the space provided for thecarrier 302 to move, the mechanics of the linkages 306 and theperformance of the actuators 304. The practical angular limit in theplane parallel to the catheter 12 is 180 degrees or less. The practicalrange 332 of the system is governed by the frequency of the ultrasoundsignal and other characteristics of the transducers 4 and theircontroller 28 but is sufficient to visualize the body lumen 100 andimmediate surroundings. These factors also have an effect on theresolution of the system.

FIG. 13 illustrates the three-dimensional imaging volume of the singleultrasound transducer array 4, oscillating circumferentially through a90-degree angle (45 degrees clockwise and 45 degrees counterclockwise)and simultaneously rocking through a 60-degree angle (30 degrees forwardand 30 degrees backward). In this embodiment, the catheter 12 comprisesthe single transducer ultrasound array 4 and the central lumen 18. Asthe array 4 is rotated and rocked, a three-dimensional field of view orimaging volume 340 is obtained. The imaging volume 340 is bounded by therange 332 of the transducer array 4, two 90-degree wedges and two60-degree wedges. Additionally, there is an area where no information isacquired comprising a dead or blind volume 342. The blind volume 342 isthe sphere enclosing the array 4 with the range 332 minus the imagingvolume 340. These representative specifications are appropriate to allowfor monitoring of endovascular therapies. However, the angularspecifications may significantly differ from those shown and still beuseful and appropriate.

FIG. 14A illustrates the three-dimensional imaging volume 340 ofcatheter 12. In this embodiment, sufficient transducers 4 are rotatedthrough a circumferential angle sufficient to fill in the gaps or blindzones between the transducers 4. For example, if four transducers 4 areused, a circumferential rotation angle of 90-degrees or greater wouldsuffice to render a complete 360-degree image. Six transducers 4 wouldrequire a 60-degree or greater circumferential rotation angle. The arrayof ultrasound transducers 4 are also rocked or pivoted axially through a60-degree angle. The resulting three-dimensional imaging volume 340 is atoroid bounded by the range 332 of the transducers 4 and constrainedwithin a 60-degree wedge shaped longitudinal section.

FIG. 14B shows the three-dimensional imaging volume 340 of catheter 12where axial rocking occurs through a greater angle than in FIG. 14A. Inthis embodiment, sufficient transducers 4 are rotated through acircumferential angle sufficient to fill in the gaps or blind zonesbetween the transducers 4. Additionally, the transducer array 4 isrocked axially through a 180-degree angle. The resultingthree-dimensional imaging volume 340 is a sphere centered about theultrasound array 4 and bounded by the range 332 of the ultrasoundtransducers 4. In this embodiment, there are no blind zones within therange 332 of the transducers 4.

FIG. 15 and FIG. 16 show the tip 2 of the catheter 12 with the addedfeatures of the inflation lumen 350, the non-distensible dilatationballoon 22, a stent 354 and a radiopaque marker 356. Referring to FIG.15, the balloon 22 and the stent 354 are collapsed to be able to passthrough the body lumen 100 to the target site. In this embodiment, theballoon 22 is positioned on the catheter tip 2, over the transducerarray 4, to be able to image the balloon 22 and stent 354 duringinflation and deployment or retrieval. Deployment or retrieval ofresiliently expandable stents 354 or devices would be similarlymonitored with this system. The radiopaque marker 356 allows forvisualization of the catheter under fluoroscopy and X-ray. Theradiopaque marker 356 in one embodiment is designed to provideorientation information for the catheter in the circumferentialdirection. Typically, the radiopaque marker 356 is fabricated fromtantalum, platinum or the like.

FIG. 16 shows the tip 2 of the catheter 12 with the balloon 22 and thestent 354 expanded. Expansion occurs through the application ofhigh-pressure fluid, preferably water, saline, or radiopaque contrastmaterial to the interior of the balloon 22, which is accessed by theinflation lumen 350. Referring to FIG. 3 and FIG. 16, the high pressureis generated by the inflation system 38, such as a syringe, connected atthe proximal end 16 of the catheter 12 to the inflation port 36, whichconnects to the balloon 22 through the inflation lumen 350.

FIG. 17 illustrates the distal end of an imaging catheter 400 comprisinga catheter shaft 402 with a proximal and a distal end, a plurality ofimaging transducers 414 and 416 that are vibrated rotationally and,optionally, rocked in a plane parallel to the long axis of the cathetershaft 402. The imaging catheter 400 further comprises a delivery lumen406, an embolic coil 408, a pusher 412, a releasable link 410, and aradiopaque marker 404. The anatomy into which the embolic coil 408 isbeing deployed comprises the parent vessel 420, the aneurysm sac 422,and blood 424. An exemplary field of view 418 of transducer 414 is alsoillustrated.

The pusher 412 extends from the distal end of the catheter 400 to theproximal end and the operator pushes on the pusher 412 to move theembolic coil 408 along the delivery lumen 406 and out near the distalend of the catheter 400. The releasable link 410 is activated to unhookthe embolic coil 408. The pusher 412 is then withdrawn out of theproximal end of the catheter 400 and a new coil 408, attached to apusher 412 by a releasable link 410, is now advanced into the proximalend of the delivery lumen 406.

Referring to FIG. 17, the method of aneurysm or arteriovenousmalformation embolization comprises the steps of first placing aguidewire or guide catheter endovascularly into the cerebrovasculature.The real time 2-D or 3-D ultrasound imaging array is advanced eitherover the guidewire or through one or more guiding catheters to thelocation of the aneurysm under fluoroscopic guidance. The ultrasoundimaging array catheter 400 comprises a lumen for delivery of embolicmaterial such as hardenable polymers, platinum coils, gels or the like.In another embodiment, a catheter separate from the imaging catheter 400is used to treat the aneurysm or arteriovenous malformation by deployingthe embolic material. With two separate catheters, close proximitybetween the imaging region of the imaging catheter and the distal end ofthe treatment catheter are beneficial. Under direct visualization of theaneurysm 422, as imaged by the catheter 400, the embolic material 408 isdeployed through the delivery lumen 406 into the aneurysm 422. Completetreatment and interrogation of the result is completed using the imagingarray 414 and 416. Additional embolic material is deployed as required.The imaging and treatment catheters are removed.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is therefore indicatedby the appended claims rather than the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. An imaging device for emitting ultrasonic acoustic waves andproviding a useable image in response to detection of reflections ofsaid acoustic waves, said imaging device comprising: an axially elongatestructure adapted for insertion into a body lumen or cavity; an array ofoutwardly directed transmitting transducer elements mounted to saidstructure for electrically generating a plurality of output ultrasonicacoustic waves; a first linear actuator operably connected to saidstructure for rotationally vibrating said array of transducer elementscircumferentially around the longitudinal axis of the axially elongatestructure, wherein the first linear actuator is affixed to saidstructure proximate the distal end of the structure; a second linearactuator operably connected to said structure for rotationally vibratingsaid array of transducer elements around an offset axis, the offset axisoffset from the longitudinal axis of the axially elongate structure,wherein the second linear actuator is affixed to said structureproximate the distal end of the structure; a cable connecting saidstructure to an environment external of said lumen and including atleast one signal channel for transporting electrical signals; at leastone receiving transducer mounted on said structure and proximate to saidarray of transmitting transducer elements for receiving reflections ofsaid output ultrasonic acoustic waves from said array of transducerelements and converting said reflection ultrasonic acoustic waves toreflection electrical signals that are transmitted along at least one ofsaid signal channels in said cable; a processor responsive to saidreflection electrical signals from said cable for providing imaging datafrom said reflection electrical signals; a display responsive to saidimaging data for providing a visual image of said body lumen or cavityand its surrounding structure; and an element disposed at the distal tipof the axially elongate structure, adapted for performing endovascularmedical intervention.
 2. The device of claim 1 wherein said linearactuator is constructed from shape memory materials.
 3. The device ofclaim 1 wherein said linear actuator is comprised of nitinol.
 4. Thedevice of claim 1 wherein said axially elongate structure includes alumen for withdrawal of excised material.
 5. The device of claim 1wherein said axially elongate structure includes a lumen for infusing orwithdrawing fluids.
 6. The device of claim 1 wherein said axiallyelongate structure includes an inflatable balloon and at least one lumenfor inflation and deflation of said balloon.
 7. The device of claim 1wherein said axially elongate structure includes a lumen for passage ofa guidewire.
 8. The device of claim 1 further comprising a holographicor three-dimensional visual output device.
 9. The device of claim 1further comprising an element disposed proximate the distal end of theaxially elongate structure to actively provide radiation or energy inthe electromagnetic range from gamma rays to radio frequencies directedtoward the body lumen or cavity.
 10. The device of claim 1 furthercomprising a cutting element disposed at the distal tip of said axiallyelongate structure.
 11. The device of claim 1 further comprising anembolic implant device and delivery system.
 12. A method of imagingcharacteristics of a body lumen or cavity and surrounding structureusing a catheter assembly provided with an outwardly directed, radialscanning array of transducer elements and an actuator which are locatedat the end of a transmission line, said method comprising the steps of:inserting a catheter assembly into a body lumen or cavity; emittingultrasonic signals into said body lumen or cavity and surroundingstructure by selectively exciting an array of at least one transducerelement; sending electrical signals to at least two linear actuators,said linear actuators being operably connected and proximate to thetransducer array, said linear actuators rotationally oscillating saidarray of transducer elements about two axes to intermediate scanpositions with respect to an initial imaging position, the oscillationbeing relative to a proximal region of said catheter; receivingreflections of said ultrasonic signals impinging on at least one of saidtransducer elements; converting said reflection ultrasonic signals toreflection electrical signals suitable for transmission on saidtransmission line; transmitting said reflection electrical signals onsaid transmission line to an area external to said body lumen or cavity;processing said reflection electrical signals into image data; and usingsaid imaging data to guide said catheter so as to perform atherectomy,thrombectomy, electromagnetic radiation therapy, or endovascular medicalintervention of the body lumen or cavity.
 13. The method of claim 12wherein said method includes displaying said image data on a visualdisplay.
 14. The method of claim 12 wherein acquisition of the imagedata is substantially independent of motion of the shaft of saidcatheter and further comprises the step of generating substantiallyreal-time three-dimensional images from the image data.
 15. A cathetercomprising an outwardly directed radial scanning intraluminal ultrasoundarray of transducers; said ultrasound array of transducers being drivenby a first actuator to rotationally vibrate about a first axis tointermediate radial scan positions with respect to an initial imagingposition; said first actuator being physically located near the array oftransducers; said ultrasound array of transducers being further drivenby a second actuator to rotationally vibrate about a second axis,wherein the second axis is different from the first axis, and whereinthe second actuator is physically located near the array of transducers;and said catheter being configured for monitoring endovascular therapybeing delivered to a patient by means of ultrasound imaging.
 16. Thecatheter of claim 15 wherein said endovascular therapy is monitored bythe catheter in real time.
 17. The catheter of claim 15 furthercomprising elements for performing endovascular therapy.
 18. Thecatheter of claim 15 wherein said endovascular therapy is delivered by adifferent catheter.
 19. The catheter of claim 15 further comprising atissue cutting element disposed proximate the distal end of the axiallyelongate structure.
 20. The catheter of claim 15 further comprising anelement disposed proximate the distal end of the axially elongatestructure to actively provide radiation or energy in the electromagneticrange from gamma rays to radio frequencies directed toward the bodylumen or cavity.